Turbines

ABSTRACT

A vapor turbine arrangement comprising a turbine having a plurality of bladed rotor wheels and provided with means for extracting liquid entrained within the vapor passing through the main vapor flow path of the turbine, which means are positioned to extract the liquid at a stage of the vapor expansion within the turbine upstream of a final bladed rotor wheel at the low pressure end of the turbine and which extract a portion of the vapor together with the liquid, the arrangement further having means for the return of the vapor to the main vapor flow path of the turbine, subsequent to separation of the vapor and liquid, at a stage of the vapor expansion within the turbine where the pressure of the vapor is only slightly lower than the pressure at which it was extracted, the vapor being returned to up-stream of at least one bladed rotor wheel of the turbine.

United States Patent [191 Bolter TURBINES [75] Inventor: John ReginaldBolter, Durham,

England [73] Assignee: Reyrolle Parsons Limited, Durham,

England [22] Filed: June 14, 1971 [21] Appl. No.: 152,557

[30] Foreign Application Priority Data June .15, 1970 Great Britain28,905/70 [52] US. Cl 415/121 A, 415/101, 415/168 [51] Int. Cl. F0ld25/32, F01d 3/02 [58] Field of Search 415/121 A, 168, DIG. 1,

[56] References Cited UNITED STATES PATENTS 2,181,752 11/1939 Warren415/168 3,066,912 12/1962 Scheper, Jr. 415/121 A FOREIGN PATENTS ORAPPLICATIONS 993,476 5/1965 Great Britain 415/168 June 12, 19731,115,125 12/1955 France ..415/168 Primary Examiner-Henry RaduazoAttorney-Holman & Stern 57 ABSTRACT A vapor turbine arrangementcomprising a turbine having a plurality of bladed rotor wheels andprovided with means for extracting liquid entrained within the vaporpassing through the main vapor flow path of the turbine, which means arepositioned to extract the liquid .at a stage of the vapor expansionwithin the turbine upstream of a final bladed rotor wheel at the lowpressure end of the turbine and which extract a portion of the vaportogether with the liquid, the arrangement further having means forthereturn of the vapor to the main vapor flow path of the turbine,subsequent to separation of the vapor and liquid, at a stage of thevapor expansion within the turbine where the pressure of the vapor isonly slightly lower than the pressure at which it was extracted, thevapor being returned to up-stream of at least one bladed rotor wheel ofthe turbine.

6 Claims, 2 Drawing Figures PAIENIEBJUNI 2m 7 3,738,770

SHEEI 1 0f 2 lb I7 I8 I9 OZI Z2 23 I 28 INVENTOR JOHN REGINALD BOLTERPAIENI Emummn 5738370 SHEEI 2 0F 2 INVENTOR JOHN REGINALD BOLTER 1TURBINES This invention relates to vapor turbines and is particularlyconcerned with such turbines designed to operate under conditions whereboth vapor and liquid are present in the turbine.

PRIOR TECHNIQUES It is common practice in the steam turbine art toprovide means for removal of water from such turbines, both toreducethermodynamic losses and to reduce damage to the turbine due tothe presence of water.

In axial-flow steam turbines the extraction means are generally providedat the wall of an annular chamber surrounding a rotor blade ring, and itis known, furthermore, that extraction of steam in addition to water insuch an arrangement assists in'the removal of water, the degree to whichit does so varyingconsiderably with the design of the extraction means.In known arrangements, therefore, water extraction means are arranged tocoincide with bled steam extraction areas, or belts as they are oftenreferred to, the extracted water and steam passing to a feed waterheater or some other apparatus in which its thermodynamic potential canbe utilized. In such arrangements the pressure of steam at the bledsteam extraction belt is sufficiently low that the steam and water canbe passed directly to, for example, a feed water heater. Bled steamextraction arrangements have consequently been applied only inintermediate and low pressure turbines and towards the final, lowerpressure, blading stages-in high pressure turbines.

If steam were to be taken from the turbine'at some point of highpressure in the expansion relative to the turbine exhaust pressure, forpassage to some apparatus at a lower pressure, such as a feed waterheater, or for water extraction purposes, or for both purposes, it wouldhave to be throttled resulting in-a loss of efficiency in the steamcycle which could outweigh the advantage gained by removal of water fromthe turbine. High pressure turbines using superheated steam at highpressures and temperatures donot present any problems as regards waterextraction since the steam is in a dry condition throughout itsexpansion within the turbine. In certain types of power plant'however,for instance a water cooled nuclear reactorplant, turbines may berequired to operate with saturated steam at relatively low pressurecompared with that of superheated steam for high pressure turbinesoperating with dry steam, but at a sufficient pressure, nevertheless, to

' cause bled steam extraction from the higher pressure blading stages tolower pressure apparatus to be aninefficient process.

SUMMARY OF THE INVENTION The invention consists in a vapor turbinearrangement comprising a turbine having a plurality of bladed rotorwheels and provided with means for extracting liquid entrained withinthe vapor passing through the main vapor flow path of the turbine, whichmeans are positioned to extract the liquid at a stage of the vaporexpansion within the turbine upstream of a final bladed rotor wheel atthe low pressure end of the turbine and which extract a portion of thevapor together with the liquid, the arrangement further providing forthe return of the vapor to the main vapor flow path of the turbine,subsequent to separation of the-vapor and liquid, at a stage of thevapor expansion within the turbine where the pressure of the vapor isonly slightly lower than the pressure at which it was extracted, thevapor being returned up-stream of at least one bladed rotor wheel of theturbine.

Turbine arrangements in accordance with the invention may make use ofany vapor/liquid separation equipment in which loss of pressure in thevapor in passing through the equipment is small, for example centrifugalseparators of the type described in our (copending British Patentapplication No. 40050/68 now Patent No. 1,283,355). The invention isparticularly useful in steam turbines where the efficiency of the waterextraction system employed is improved by the extraction of steam also,as is the case with the afore mentioned co-pending application in whicha slotted circumferentially extending drainage area is employed; and asis also the case with water extraction systems in corporated within aturbine casing of the type disclosed in (our co-pending British Patentapplication N o. 39987/68 now Patent No. 1,283,044).

While the invention may be applied in single flow turslightly lower aresimply achieved.

Accordingly, the invention further consists in a vapor turbinearrangement in accordancewith the first of the preceding threeparagraphs, in which the turbine is of the multi-flow type having atleast two main flow paths for motive fluid through the turbine, liquidand vapor being extracted from a first main vapor flow path of theturbine and the vapor being returned to a second main vapor flow path ofthe turbine, subsequent to separation of the vapor and liquid, at astage of the vapor expansion within the second main vapor flow pathwhere the pressure of the vapor is only slightly lower than the pressureat which it was extracted from the first main vapor flow path.

The invention further consists in a vapor turbine arrangement inaccordance with the preceding paragraph in which one or more extractionsof liquid and vapor and return of vapor per main vapor flow path aremade.

The invention also consists in a vapor turbine arrangement in accordancewith either of the preceding two paragraphs in which vapor/liquidseparation is effected within the turbine casing.

The invention also consists in a vapor turbine arrangement in accordancewith any of the preceding three paragraphs in which the blade paths ofthe first rangement in accordance with the preceding paragraph I inwhich blades of at least a portion of the blade path in the first mainvaporflow path are made to differ in length from the blades in acorresponding section of the f blade path in the second main vapor flowpath.

The invention also consists in a vapor turbine ar-' rangement inaccordance with the first of the preceding two paragraphs in which theblade openings of at least" a portion of the blade path in the firstmain vapor flow path are made to differ in width from the blade open-BRIEF DESCRIPTION THE DRAWINGS FIG. 1 shows a cross-section through adouble-flow steam turbine in accordance with the preferred form of theinvention; and

FIG. 2 shows a simplified side-elevation of the turbine shown in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIG. 1, theturbine shown comprises a rotor l and a stator made up of an outercasing 2 and inner sections 3a-3e.

The rotor is provided with ten blade wheels to each side of the centerline X-X of the turbine, blade wheels 4-13 lying in a first main flowpath for steam entering centrally at annular chamber 14 and exhaustingat left-hand chamber 15, while blade wheels 16-25 lie in the second mainflow path for steam which also enters at chamber 14 but exhausts atright-hand chamber 26. Each rotor blade wheel is immediately preceded inthe steam flow path by a stator blade wheel, as shown, the stator bladewheels being carried by sections 3a-3e.

The turbine shown is intended for use with steam which is substantiallywet after the fourth rotor blade wheel in each flow is reached, that isto say at the points indicated by reference numerals 27 and 28 in FIG.1, and may, for example, be a high pressure turbine powered by steamfrom a water cooled nuclear reactor.

In accordance with the present invention, water and steam are extractedfrom the region of point 27 following the fourth rotor blade stage inthe left-hand flow, preferably by way of louvred extraction belts inaccordance with out afore-mentioned British Patent No. 1,283,044 themixture entering an annular chamber 29.

The mixture is next led by way of an external pipe 30, as shown in FIG.2, to a steam/water separator 31, which may be of the centrifugal typeas disclosed in our afore-mentioned British Patent No. 1,283,355, afterwhich the dried steam passes by way of pipe 32 to an annular chamber 33in the right-hand stator casing. The steam is then led into therighthand flow in the region of point 28 so that it may do useful workin the fifth and successive blade wheels of the right-hand side of theturbine.

The blade paths of blade wheels 4-7 in the left-hand flow and bladewheels 16-19 in the right-hand flow are designed so that the pressure atpoint 28 is slightly less, of the order of less, say, than the pressureat point 27, and this small difference in pressure is sufficient tocause the steam to flow through pipes 30 and 32 and separator 31. Thepressure difference may be achieved by making the blades ofcorresponding blade wheels in the two flows of different lengths, or byvariations in the openings of the blades of the corresponding wheels.

Further drying of the steam may be achieved by repeating the processdescribed at a later stage of the steam expansion. As shown in thefigures, steam and water may be removed from the right-hand flow atannular chamber 34, dried in a separator 35, and returned to theleft-hand flow by way of annular chamber 36.

In the form of the invention shown, a baffle 37 serves to separate steamat different pressures in the chambers 29 and 33. In alternative formsof the invention not shown, the steam/water separator apparatus may beincluded within the stator outer casing 2 in which case the baffle 37may be omitted. The combined annular chamber so formed may be fittedwith baffles to promote separation of the water and steam and the waterthen allowed to drain from the chamber. Whichever system of steam/waterseparation is used, the water extracted would normally be fed to a feedheater or other apparatus by way of control orifices and a flashbox.

While the form of the invention shown incorporates two extractions andreturns per flow, there may be any number of such drying arrangementsincorporated in a single turbine, the number being limited in practiceby the space available for conduction of the flows and economicconsiderations.

While turbine arrangements according to the invention are particularlyuseful for axial-flow steam turbines operating with steam which is wetor becomes wet within a high pressure cylinder, the invention is notrestricted to such operation but may be used in vapor turbines driven byfluids other than steam and where the effective vapor flow is other thanaxial.

I claim:

1. A vapor turbine arrangement comprising a turbine having a pluralityof bladed rotor wheels and provided with means for extracting liquidentrained within the vapor passing through the main vapor flow path ofthe turbine, which means are positioned to extract the liquid at a stageof the vapor expansion within the turbine upstream of a final bladedrotor wheel at the low pressure end of the turbine and which extract aportion of the vapor together with the liquid, the arrangement furtherhaving means for the return of the vapor to the main vapor flow path ofthe turbine, subsequent to separation of the vapor and liquid, at astage of the vapor expansion within the turbine where the pressure ofthe vapor is only slightly lower than the pressure at which it wasextracted, the vapor being returned up-stream of at least one bladedrotor wheel of the turbine, the turbine being of the multi-flow typehaving at least two main flow paths for motive fluid through theturbine, liquid and vapor being extracted from a first main vapor flowpath of the turbine and the vapor being returned to a second main vaporflow path of the turbine, subsequent to separation of the vapor andliquid, at a stage of the vapor expansion within the second main vaporflow path where the pressure of the vapor is only slightly lower thanthe pressure at which it was extracted from the first main vapor flowpath.

2. The vapor turbine arrangements as claimed in claim 1, in which morethan one extraction of liquid and vapor and more than one return ofvapor per main vapor flow path are made.

3. The vapor turbine arrangement as claimed in claim 1, in whichvapor/liquid separation is effected within the turbine casing.

4. The vapor turbine arrangement as claimed in claim 1, in which theblade paths of the first and second main flow paths are designed tointroduce the required difference in pressure of the vapor in theturbine between an extraction point in the first main flow path and acorresponding return point in the second main flow path.

5. The vapor turbine arrangement as claimed in claim 4, in which bladesof at least a portion of the blade path in the first main vapor flowpath are made to differ in 3 ,73 8 ,770 5 6 length from the blades in acorresponding section of the made to differ in width from the bladeopenings in corblade path in the main vapor w responding sections of theblade path in the second 6. The vapor turbine arrangement as claimed 1nclaim 4, in which the blade openings of at least a portion of main vaporflow path the blade path in the first main vapor flow path are 5

1. A vapor turbine arrangement comprising a turbine having a pluralityof bladed rotor wheels and provided with means for extracting liquidentrained within the vapor passing through the main vapor flow path ofthe turbine, which means are positioned to extract the liquid at a stageof the vapor expansion within the turbine upstream of a final bladedrotor wheel at the low pressure end of the turbine and which extract aportion of the vapor together with the liquid, the arrangement furtherhaving means for the return of the vapor to the main vapor flow path ofthe turbine, subsequent to separation of the vapor and liquid, at astage of the vapor expansion within the turbine where the pressure ofthe vapor is only slightly lower than the pressure at which it wasextracted, the vapor being returned up-stream of at least one bladedrotor wheel of the turbine, the turbine being of the multi-flow typehaving at least two main flow paths for motive fluid through theturbine, liquid and vapor being extracted from a first main vapor flowpath of the turbine and the vapor being returned to a second main vaporflow path of the turbine, subsequent to separation of the vapor andliquid, at a stage of the vapor expansion within the second main vaporflow path where the pressure of the vapor is only slightly lower thanthe pressure at which it was extracted from the first main vapor flowpath.
 2. The vapor turbine arrangements as claimed in claim 1, in whichmore than one extraction of liquid and vapor and more than one return ofvapor per main vapor flow path are made.
 3. The vapor turbinearrangement as claimed in claim 1, in which vapor/liquid separation iseffected within the turbine casing.
 4. The vapor turbine arrangement asclaimed in claim 1, in which the blade paths of the first and secondmain flow paths are designed to introduce the required difference inpressure of the vapor in the turbine between an extraction point in thefirst main flow path and a corresponding return point in the second mainflow path.
 5. The vapor turbine arrangement as claimed in claim 4, inwhich blades of at least a portion of the blade path in the first mainvapor flow path are made to differ in length from the blades in acorresponding section of the blade path in the second main vapor flowpath.
 6. The vapor turbine arrangement as claimed in claim 4, in whichthe blade openings of at least a portion of the blade path in the firstmain vapor flow path are made to differ in width from the blade openingsin corresponding sections of the blade path in the second main vaporflow path.